Computational wear of knee implant polyethylene insert surface under effects of real dynamic loadings, posterior tibial slope variation and anterior-posterior translation with interior-exterior rotation

The effect of posterior tibial slope on the maximum contact pressure and wear volume of polyethylene (PE) insert were not given special attention. In order to determine the effects of flexion angle, Anterior-Posterior (AP) translation, Internal-External (IE) rotation and Tibial slope on the max contact pressure and wear of PE insert of Total Knee Artroplasty (TKA) were investigated under loadings which were obtained in cadaver experiments by using Archard's wear law. This study uses not only loads obtained from cadaver experiments but also dynamic flexion starting from 0 to 90 degrees. Wear on knee implant PE insert was investigated using a 2.5 size 3 dimensional (3D) cruciate sacrificing total knee replacement model and Finite Element Method (FEM) under loadings and AP Translation data ranging from 0 to 90 flexion angles validated by cadaver experiments. Two types of analyses were done to measure the wear effect on knee implant PE insert. The first set of analyses included the flexion angles dynamically changing with the knee rotating from 0 to 90 angles according to the femur axis and the transient analyses for loadings changing with a certain angle and duration. It is seen that the contact pressure on the PE insert decreases as the cycle increases for both Flexion and Flexion+AP Translation. It is clear that as the cycle increases, the wear obtained for both cases increases. The loadings acting on the PE insert cannot create sufficient pressure due to the AP Translation effect at low speeds and have an effect to reduce the wear, while the effect increases with the wear as the cycle increases, and the AP Translation now contributes to the wear at high speeds. It is seen that the IE rotation has a much more effect on the wear of the insert than the AP translation, especially as the number of revolutions increases, it significantly reduces the wear on the insert, and this effect is due to the enlargement of the wear zone. It is also seen that as the posterior tibial slope angle increases, the maximum contact pressure values slightly decrease for the same cycle. This study indicated that AP Translation, which changes direction during flexion, and IE Rotation, which doing angular changes, had a significant effect on both contact pressure and wear. Unlike previous similar studies, it was seen that the amount of wear continues to increase as the cycle increases. This situation strengthens the argument that AP translation and IE rotation values that change with loading and flexion shape the wear effects on PE Insert.